1. Field of the Invention
The invention relates to a matrix multiplier for use in computations in which the operands are in analog format and in which the terms of the matrix are fixed and assume both positive and negative values. The matrix multiplier is designed for processing sampled analog data supplied to paralleled inputs representing an input vector and produces output data on paralleled outputs at the sampling rate, corresponding to an output vector. The output vector is proportional to the product of the matrix of stored values and the input vector. An important application of the invention is to the computation of the Discrete Fourier Transformation.
2. Description of the Prior Art
A number of matrix multipliers have been described in the prior art. When the devices require digital inputs, the raw data, usually in the analog format, must be converted to digital format at the input of the processor. In addition, in digital format, multiplication causes word growth with accompanying delays which force one to add active or passive storage to compensate for the processing time. In computations of the Fast Fourier Transform, it is known to store the complex trigonometric weights in a memory, which is accessed for processing with the input data. One such approach is described in the U.S. Pat. No. 4,020,334, entitled "Integrated Arithmetic Unit for Computing Summed Indexed Products" of Noble R. Powell and John M. Irwin and assigned to the Assignee of the present invention.
An implementation of the Discrete Fourier Transform using the charge coupled device has been suggested using the chirp "Z" algorithm, IEEE Transactions of Audio and Acoustics, Volume AU-17, #2, June 1969. The implementation of the chirp "Z" algorithm with charge coupled devices requires four correlator channels preceded by a complex multiplication by certain trigonometric weights. This operation is then followed by a "de-chirp" filter again requiring complex trigonometric weights. In this implementation, also the total circuit requirements are complex.